File content as of revision 0:5a419ba2726d:

/*
Copyright 2013 Paul Soulsby www.soulsbysynths.com
    This file is part of Atmegatron.

    Atmegatron is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Atmegatron is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Atmegatron.  If not, see <http://www.gnu.org/licenses/>.
*/

//***15 Biquad filter algorithms***

#ifndef __FILTER_H__
#define __FILTER_H__


//the filter types
#define FILT_OFF 0
#define FILT_LPF 1
#define FILT_HPF 2
#define FILT_BPF 3
#define FILT_NOTCH 4
#define FILT_PEAK10 5
#define FILT_PEAK30 6
#define FILT_PEAK100 7
#define FILT_LS10 8
#define FILT_LS30 9
#define FILT_HS10 10
#define FILT_HS30 11
#define FILT_BUTLPF 12
#define FILT_BUTHPF 13
#define FILT_BESLPF 14
#define FILT_BESHPF 15

//These constants are used to define the MAXIMUM amount the env and lfo can effect the filter cutoff.
//The default max (for both env and lfo) is: 
//********multiplier = 4***********
#define FILT_MAX 1.386294361119891f  //ln(multiplier)
#define FILT_MULT 64                 //multipler used for calculating lookup table  (256 / multiplier)  
#define FILT_BS 6UL                  //bitshift amount when multiplying fc by filt lfo amt.  log2(FILT_MULT)

#define SQRT2 1.414213562373095f    //squareroot 2 - useful!
#define PI  3.141592653589793f

#define MINQ 0.5f                  //minimum value of Q (default = 0.5)
#define MULTQ 0.076470588235294f   //multiplier to convert from filt_q(0-255) to real Q (0.5-20) = (20 - 0.5)/255;

#define abs(a)  (a)>=0? (a) : -(a)


void Filt_Let_Fc(byte newfc);
byte Filt_Get_Fc(void);
void Filt_Let_Q(byte newq);
byte Filt_Get_Q(void);
void Filt_Let_Type(byte newtype);
byte Filt_Get_Type(void);
void Filt_Let_GainAdj(boolean newadj);
boolean Filt_Get_GainAdj(void);
void Filt_CalcVals(void);
void LPValCalculator(void);
void HPValCalculator(void);
void BPSkirtValCalculator(void);
void NotchValCalculator(void);
void PeakingEQValCalculator(void);
void LowShelfValCalculator(void);
void HighShelfValCalculator(void);
void ButterworthLPCalculator(void);
void ButterworthHPCalculator(void);
void BesselLPCalculator(void);
void BesselHPCalculator(void);
void Filt_Process(void);
float Biquad_process(float bi0);
void Filt_Let_LFOAmt(byte newamt);
byte Filt_Get_LFOAmt(void);
byte Filt_Get_LFOGain(void);
void Filt_Let_FenvAmt(byte newamt);
byte Filt_Get_FenvAmt(void);
byte Filt_Get_FenvGain(void);


#endif // __FILTER_H__